The market for plant protein concentrates as nutritional supplements is large and growing. Unlike protein concentrates derived from some other plants, such as soybeans, protein concentrates derived from yellow field peas have the advantage of being hypoallergenic. Unfortunately, yellow pea protein concentrates having a complete essential amino acid profile, a digestibility score of 1.00, and Protein Digestibility Corrected Amino Acid Score (PDCAAS) of 1.00 are not currently available.
Certain cultivars of yellow peas naturally contain the correct amino acid profile to meet one of the age categories for a complete amino acid profile, as published by the Food and Agricultural Organization of the United Nations/World Health Organization (FAO/WHO). However, the digestibility of yellow field peas is relatively low, with typical Digestibility Scores of 0.61-0.74, primarily due to the presence of low digestible proteins (e.g., prolamins and glutelins), fibers, and the influence of anti-nutritional factors. (See, Field Peas: Chemical Composition and Energy and Amino Acid Availabilities for Poultry”, Canadian Journal of Animal Science, 1997 and the Canadian Field Pea Industry Guide, Third Edition, 2003 and Leterme et al. in the Journal of the Science of Food and Agriculture, vol. 53 pp. 107-110 (1990).) Moreover, the processing techniques presently used to extract, isolate, and concentrate pea proteins from yellow peas result in concentrates that do not have a complete essential amino acid profile, even when they are derived from yellow pea pulses that may have a complete essential amino acid profile.
The processes currently being used for the production of protein concentrates from yellow field peas and flours produced therefrom generally include three steps: 1) aqueous protein extraction, 2) separation of water-insoluble materials, and 3) a final separation of water-soluble non-protein components from the proteins. The protein extraction (Step 1) is performed in one of three processes: alkaline pH extraction, wherein the pH of a yellow pea/water slurry is increased by adding sodium, potassium, or calcium hydroxide; fermentation with lactic acid or other bacteria; or salt extraction, wherein a specific ionic strength of salt is added to take advantage of the salting-in and salting-out phenomena of proteins. In Step 2, the major portion of the water-insoluble, non-protein components of starch, crude fiber, sugars, non-starch polysaccharides, oligosaccharides, fat, and ash are removed from the protein extracts from Step 1 by separating the insoluble materials from the water phase using physical methods such as settling, decanting, centrifuging, filtrating, or screening to provide a protein-enriched extract and an insoluble co-product. In Step 3, the protein-enriched extract obtained in Step 2 is further processed to separate the water-soluble proteins from other water-soluble non-protein components in the protein-enriched extract. This step is most commonly carried out using an isoelectric precipitation (also referred to as acid precipitation).
To address the deficiencies in the essential amino acid profiles of pea protein concentrates made using conventional processing techniques, producers have resorted to blending together concentrates derived from different protein sources (with different limiting amino acid compositions) to create a product which has a blended amino acid profile that meets the industry standards for a complete amino acid profile. For example, typically companies would blend pea and rice proteins together, as rice is high in sulfur-containing amino acids and low in lysine; whereas, pea is high in lysine and low in sulfur-containing amino acids. For example, U.S. patent application publication number 20080206430, “Compositions Consisting of Blended Vegetarian Proteins” identifies a protein blend of soy, peas, and rice proteins blended in specific proportions to obtain a protein product with a blended amino acid of 1.00; even still, this blended formula does not provide a PDCAAS of 1.00 because the digestibility of the protein blend was not 1.00.